Clean up some use of __ANDROID_NDK__ in the cmake files

Rationale:
scripts/Python/modules: android is excluded at a higher level, so no point in
  checking here
tools/lldb-mi: lldb-mi builds fine (with some cosmetic tweaks) on android, and
  there is no reason it shouldn't.
tools/lldb-server: LLDB_DISABLE_LIBEDIT/CURSES already take the platform into
  account, so there is no point in checking again.

I am reasonably confident this should not break the build on any platform, but
I'll keep an eye out on the bots.

llvm-svn: 288661